With midterm elections days away and Central American migrants plodding northward, President Trump is deploying more than 7,000 active-duty troops to support border agents. He's also vowed to further limit asylum and put up massive tents to detain asylum-seekers who get caught crossing illegally. NPR's John Burnett sent us this report from South Texas.

JOHN BURNETT, BYLINE: The president's dire warnings of an imminent invasion of dangerous Central American immigrants has gotten people's attention here in the gritty border town of Progreso, Texas. This week, big steel gates were installed on the international bridge leading to Nuevo Progreso, Mexico. They can swing shut in case immigrants try to storm the U.S. port of entry, something that's never happened before.

RUBEN TREVINO: I've been coming here for 20 years, and they have never, ever been any gates like that. When we walked by today and we saw the gates, we were in shock.

BURNETT: That's Ruben Trevino walking home from Nuevo Progreso after he and his wife visited a dentist in Mexico. Most of a dozen bridge crossers interviewed say they're glad the authorities put in gates to keep out unwanted immigrants. Bob and Sharon Caylor moved to South Texas from Michigan. They were also seeing a Mexican dentist and buying meds.

SHARON CAYLOR: Yeah, it's a good idea. But I don't think the caravan's going to make it.

BURNETT: Why not?

S. CAYLOR: Well, they got 900 more miles to go. They're going to wear their shoes out. They're getting sick.

BOB CAYLOR: I think that they ought to put crocodiles in the river.

S. CAYLOR: Not crocodiles, alligators.

B. CAYLOR: Alligators.

BURNETT: Earlier this week, the Pentagon released details of its deployment. More than 7,000 troops are coming from across the country - helicopter companies to move Homeland Security personnel, engineer battalions to build vehicle barriers and fencing, medical teams to treat casualties. Trump already sent more than 2,000 National Guard to the border earlier this year to back up federal agents. At the Brownsville VFW Hall, a 20-year Navy veteran named Juan Palomo wonders why active duty and why now.

JUAN PALOMO: You have reservists, and you have National Guard. They use them every time that there is hurricanes, flooding. What's the difference now? Why don't they use them instead of taking people who are active duty who have an - a job to do already to come down here and police the borders?

BURNETT: The main caravan is estimated to have dropped from 7,000 to fewer than 4,000 currently, and it's still in southern Mexico. But border agents say they've been swamped with migrant families for months. Chris Cabrera is a local spokesman for the agents' union.

CHRIS CABRERA: Everybody's making this huge deal about a caravan coming in. The caravan's coming. It's coming. We're getting 5,000 a week in the Rio Grande Valley - a week. That's a caravan in and of itself. It's already here. The problem's here.

BURNETT: Cabrera is on the fence about whether the troops will help. He says the real problem is the asylum process that lets applicants linger inside the U.S. for years while their cases work through the overloaded court system.

Yesterday, Trump said he plans to issue an executive order that would deny asylum to anyone who crosses unlawfully. That would mean all immigrants seeking asylum must cross at a legal port of entry. But there's already a bottleneck at border crossings from San Diego to Brownsville. A new crush of applicants could make things worse, says Michael Seifert, who works with the ACLU in South Texas. He says they watch the Brownsville-Matamoros International Bridge every day.

MICHAEL SEIFERT: Even if you wanted to come in the right way, you're going to be prepared to wait eight to 10 days out in the open in a place where there's no restroom facilities on the side of the bridge that right now is not safe because of the drug wars.

BURNETT: This unusually blustery political season has put U.S. border towns front and center. Brownsville Mayor Tony Martinez hears about the caravan supposedly coming to rush his bridges, of politicians saying they need to militarize his community to protect it and of Democrats accused of being for open borders. Martinez himself is a Democrat running for re-election next year, and he says he's just had it.

TONY MARTINEZ: It's not about open borders. It's about secure borders, and we have secure borders. We've had border walls for 20 years, you know? This rhetoric is just beyond the pale. It is so absurd. And I know that some people will believe it because they don't live here. They don't know it.

BURNETT: The mayor says, come and visit after the election. The border's not such a scary place. John Burnett, NPR News, Brownsville. Transcript provided by NPR, Copyright NPR.